1. Field of the Invention
The present invention relates to a recording head and recording apparatus performing recording in a recording medium by discharging liquid, particularly to the recording head and recording apparatus having a structure in which clogging of a discharge port is prevented by keeping a periphery of the discharge port moist.
2. Related Background Art
In a liquid discharge recording head and a liquid discharge recording apparatus on which the liquid discharge recording head is mounted (hereinafter simply referred to as “recording head” and “recording apparatus” respectively), there are various problems caused by ink (liquid) drying.
For example, when a period during which the ink is not discharged becomes longer, moisture in the ink evaporates through the discharge port, which sometimes results in an increase in viscosity of the ink in the discharge port or formation of a solid-state-like film on a surface of a meniscus in the discharge port. Thus, when the increase in viscosity of the ink or the formation of the film occurs, flow resistance of the ink is increased. Therefore, in discharge action, there are problems that discharge speed is decreased and an ink discharge direction is inclined from a predetermined direction by the influence of the solid-state-like film.
Sometimes the problem in the discharge action, which is caused by the ink drying because the ink is not discharged for a long time, is called “first discharge problem.” Particularly the problem becomes easily prominent in the current recording head in which the discharge port and an ink droplet are miniaturized in order to improve image quality.
Conventionally, countermeasures are taken against the problem by forming a configuration shown in FIGS. 5A, 5B, 6A, and 6B. FIG. 5A is a top view showing the conventional recording head, and FIG. 5B is a sectional view taken along a line VB of FIG. 5A.
The recording head, in which a region where a hydrophilic process is performed to a discharge port surface is formed, is disclosed in Japanese Patent Application Laid-Open No. 2002-331678 like a recording head 150 of FIG. 5B. In the recording head 150 of FIG. 5B, a hydrophilic process portion 115 in which the hydrophilic process is performed is partially formed in the surface (discharge port surface) of a channel forming member provided as an orifice plate. As shown in the top view of FIG. 5A, the hydrophilic process portions 115 are arranged so as to be located on both sides of a discharge port row formed by plural discharge ports 107.
When the recording head 150 having the above configuration is used by mounting the recording head 150 on the well-known recording apparatus including a suction recovery mechanism of the recording head, in performing suction recovery action, the ink remains while kept in the hydrophilic process portion 115. Then, the liquid (ink) 114 kept in the hydrophilic process portion 115 gradually evaporates, which allows high humidity to be maintained near the discharge port 107. Accordingly, the ink evaporation from the discharge port 107 is suppressed, and the period can be lengthened until the problem of the discharge action occurs. Namely, the period can be lengthened until the first discharge problem (also referred to as “first discharge time”) occurs.
Then, a recording head 250 of FIG. 6B will be described. FIG. 6A is a top view showing the recording head, and FIG. 6B is a sectional view taken along a line VIB of FIG. 6A.
In the recording head 250, liquid keeping grooves 205a are formed near a discharge port 207 such that a channel forming member 205 is bored. The liquid keeping groove 205a is opened toward the upper surface side. Moisture retention liquid such as the ink is kept in the liquid keeping groove 205a while being in the liquid state. The humidity is kept high near the discharge port 207 by the evaporation of the moisture retention liquid.
However, in the configuration shown in FIGS. 5A and 5B, the problems are generated as described below.
(1) Because an area of the hydrophilic process portion 115 is larger when compared with an amount of liquid kept in the hydrophilic process portion 115, evaporation speed of the kept liquid is fast. Therefore, it is difficult that the high humidity is kept for a long time in a periphery of the discharge port.
(2) When the surface of the channel forming member 105 is wiped with a wiping member, the liquid kept in the hydrophilic process portion 115 is also wiped. Therefore, the effect by the hydrophilic process portion 115 is not obtained.
With reference to the problem (1), the improvement can be achieved somewhat by increasing the area of the hydrophilic process portion 115. However, the recording head is enlarged, and a degree of improvement effect is not so large.
Further, in the configuration shown in FIGS. 6A and 6B, the problem is generated as described below.
(3) The liquid keeping grooves 205a are formed such that the channel forming member 205 is bored. Accordingly, a depth of the liquid keeping groove 205a is limited to a thickness of the channel forming member 205. As a result, the amount of liquid kept in the liquid keeping groove 205a cannot be increased to a sufficient extent. This means that the period is short until the liquid in the liquid keeping groove 205a evaporates completely. Consequently, it is difficult that the high humidity is kept for a long time in the periphery of the discharge port.
On the other hand, the number of liquid keeping grooves 205a is increased and the opening of one liquid keeping groove 205a is widened, which results in the sight improvement of the problem. However, there is a possibility that the improvement leads to the problem of the enlargement of the recording head. Further, even if the number of grooves is increased or the opening is widened, because the opening is separated away from the periphery of the discharge port, it is not expected that the improvement effect is sufficient.